Impact of Neurons on Group B Streptococcus Interactions at the Blood Brain Barrier

Streptococcus agalactiae (Group B Streptococcus , GBS) is a Gram-positive opportunistic pathogen and the leading cause of neonatal bacterial meningitis, a life-threatening infection of the central nervous system (CNS) that occurs when bacteria cross the blood-brain barrier (BBB). GBS commonly colonizes the maternal genital tract and is a major cause of invasive neonatal disease, including bacteremia and meningitis. Despite treatment advances, GBS meningitis remains associated with substantial mortality and long-term neurological sequelae. The BBB is a highly specialized barrier formed by brain endothelial cells (BECs) that restrict microbial entry into the CNS through tightly regulated intercellular junctions. The BBB exists within the neurovascular unit, where neurons and other CNS cell types actively regulate endothelial barrier properties through intercellular signaling. However, the contribution of neuronal-endothelial interactions to BBB function during neonatal meningitis remains poorly understood. To investigate the mechanisms by which GBS disrupts and penetrates the BBB, we utilized induced pluripotent stem cell (iPSC)-derived brain-like endothelial cells. EZ-Sphere-derived neurons generated from the same iPSC source were incorporated into an isogenic BBB model to determine whether neuronal-endothelial communication influences GBS interaction with BECs. Neuronal co-culture significantly reduced GBS adherence to and invasion of BECs while preserving tight junction integrity during infection. Application of neuron-conditioned medium similarly decreased bacterial adherence and invasion, suggesting that neuron-derived soluble factors enhance barrier integrity during GBS infection. Together, these findings demonstrate that neuronal signaling enhances BBB resistance to GBS and highlight a previously underappreciated role for neurovascular crosstalk in limiting bacterial pathogenesis.